Analysis of 27 polycyclic aromatic hydrocarbons by matrix solid-phase dispersion and isotope dilution gas chromatography-mass spectrometry in sewage sludge from the Spanish area of Madrid

A method for the determination of 27 polycyclic aromatic hydrocarbons (PAHs) in sludge from wastewater treatment plants (WWTPs) located in urban, industrial or rural zones is presented. PAHs were extracted by matrix solid-phase dispersion (MSPD) assisted by sonication. Purification of extracts was carried out by solid-phase extraction with C(18) and PAHs were eluted with acetonitrile. PAHs were determined by isotope dilution gas chromatography with electron impact mass spectrometric detection in the selected ion-monitoring mode (GC-MS-SIM), using deuterated PAHs as internal standards. The limits of detection ranged from 0.03 ng/g for acenaphthylene to 0.45 ng/g for benzo[b]naphtho[2,1-d]thyophene. After optimization, the method was validated with a certified reference sludge. The proposed analytical method was applied to determine PAH levels in sewage sludge samples collected from 19 water treatment plants located in the province of Madrid (Spain). In most of the examined samples, phenanthrene was the main compound with a mean concentration of 1062 ng/g. PAHs were detected in all of the samples, with total concentrations between 390 and 6390 ng/g dry weight for the 27 PAHs analyzed and from 310 to 5120 ng/g dry weight for the sum of the 10 PAHs considered in the draft European Union directive.     

Solid-phase clean-up in the liquid chromatographic determination of polycyclic aromatic hydrocarbons in edible oils

A solid-phase extraction (SPE) method for sample clean-up, followed by reversed-phase high-performance liquid chromatography (HPLC) with fluorescence detection is reported for the determination of polycyclic aromatic hydrocarbons (PAHs) in edible oils. The effects of experimental variables, such as washing and elution solvents, sample solvent and drying time have been studied using C18 cartridges. Recoveries and selectivity using other sorbent materials (C8, C2, CH, PH and NH2) were also examined, with C18 being the best one. The recoveries ranged between 50 and 103% depending on the molecular mass of the PAH. The limits of quantitation were lower than 1 ng/g for most PAHs and good precision was achieved. The method was validated using certified reference materials.     

Preparation, characterization and application of octadecyl modified magnesium oxide microspheres

A new solid-phase extraction sorbent, octadecyl modified magnesium oxide (C18-MgO) microspheres, was successfully prepared in the present work. Its composition, morphology and structure were studied by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N(2) adsorption-desorption technique, and solid-state nuclear magnetic resonance (NMR). The as-synthesized C18-MgO was employed as a solid-phase extraction sorbent for the enrichment of polycyclic aromatic hydrocarbons (PAHs) in aqueous solutions. Several factors affecting the extraction efficiency of PAHs, including the type and concentration of organic modifiers, flow rate, sample volume, and the types of rinsing solvents and eluting solvents, were investigated systematically. The results demonstrated that C18-MgO was superior to MgO in terms of large volume in loading samples. In comparison with MgO and Sep-Pak C18, C18-MgO exhibited excellent extraction efficiency (>91% except for naphthalene) in respect of high recoveries under the optimized conditions. The limits of detection varied from 0.001 to 0.603 ng mL(-1) for 15 PAHs using high-performance liquid chromatography coupled with a fluorescence detector, indicating that the analytical method was highly sensitive. The proposed method was applied to enrich PAHs in tap water and acceptable recoveries (18-96%) were obtained.     

Dispersive solid-phase extraction clean up combined with Soxhlet extraction for the determination of 16 PAHs in soil samples by GC-MS

Dichloromethane soil samples extracts were prepared using Soxhlet extraction technique, and after clean-up step, gas chromatography-mass spectrometry analysis of 16 priority polycyclic aromatic hydrocarbons (PAHs) was carried out. A comparison of dispersive solid-phase extraction (dSPE) and column chromatography (cC), as clean-up techniques, was evaluated. Six different sorbents (silica, diatomaceous earth, primary–secondary amine, C18, clinoptilolite and florisil) were tested as dispersive clean-up sorbents versus activated silica and alumina for cC. Best results for three concentration levels among dSPE were obtained using diatomaceous earth, with recovery values in the range of 75–112% for 13 of 16 analysed compounds, while cC recoveries were in the range of 75–111% for all analysed PAHs. Analysis of 12 soil samples from urban area of Ni? (Serbia) singled out acenaphthene as the most abundant compound.     

Use of Ce(IV) oxidizing agent for the derivatization of polycyclic aromatic hydrocarbons for liquid chromatography-electrochemical detection.

Polycyclic aromatic hydrocarbons (PAHs) were oxidized with Ce(IV), and the resulting quinones were determined by reductive-mode liquid chromatography-electrochemical detection. This oxidation is a rapid, automatable step, involving of Ce(IV) reagent to the PAH sample and cleaning up the derivative with C18 solid-phase extraction. Using a C18 analytical column and a 2-propanol-phosphate buffer as the mobile phase, detection limits were in the ppb range for naphthalene, phenanthrene and anthracene, with linearity over 3-5 orders of magnitude. Method validation was performed by addition of the PAHs to tap water and determining the levels by reference to a calibration curve. The three PAHs can be simultaneously derivatized and determined under the same chromatographic conditions. Analysis of a motor-oil sample is also shown.     

C18 functionalized graphene oxide as a novel coating for solid-phase microextraction

A novel C18 functionalized graphene oxide (GO) coated solid-phase microextraction fiber was prepared by a novel protocol. Based on the strong van der Waals interaction present in GO and abundant oxygenous groups in GO sheets, a simple layer-by-layer self-assembly method was used in the preparation process and then C18 was successfully self-assembled on GO via C-O-Si bonding. Coupled with gas chromatography, extraction performance of the fiber was tested with polycyclic aromatic hydrocarbons (PAHs) as model analytes. The fiber not only exhibited excellent extraction efficiency and selectivity, but also showed many advantages including high rigidity, long service life and well stability toward organic solvent, acidic and alkali solutions, and high temperature. The relative standard deviations for single-fiber repeatability and fiber-to-fiber reproducibility were less than 7.26 and 17.25%, respectively. The detection limits to the PAHs were less than 0.08 μg L(-1) and the calibration curves were linear in a wide range for all analytes. The as-established Solid-phase microextraction GC method was also successfully used for determination of PAHs in two real water samples.     

Comparative performance of extraction strategies for polycyclic aromatic hydrocarbons in peats

The assessment of historical trends in atmospheric deposition of organic contaminants by using peat samples has been reported on several occasions because these samples represent an almost ideal medium for recording temporal changes in organic contaminant deposition rates. The determination of polycyclic aromatic hydrocarbons (PAHs) in peat samples is complicated due to the high content of organic matter in peat, which affects both extraction efficiency and analytical quality. A rapid and simple method is proposed for the determination of 10 US Environmental Protection Agency indicator PAHs in complex matrices such as peat. This article reviews and addresses the most relevant analytical methods for determining PAHs in peat. We discuss and critically evaluate three different extraction procedures, such as ultrasound-assisted solvent extraction (UASE), shaking and pressurized liquid extraction (PLE). Clean-up of extracts was performed by solid-phase extraction using silica cartridges. Detection of the selected PAHs was carried out by high-performance liquid chromatography coupled with fluorescence detection for determination. Optimization of the variables affecting extraction by the selected extraction techniques was conducted, concluding that the UASE extraction method using hexane:dichloromethane (80:20) as extractant was robust enough to determine the selected PAHs in peat samples with estimated quantification limits between 0.050 and 3.5 μg/kg depending on the PAH. UASE did not demand sophisticated equipment and long extraction times. PLE involved sophisticated equipment and showed important variations in the results. The method proposed was applied to the determination of PAHs in peat samples from Xistral Mountains (Galicia, Spain).     

New cold-fiber headspace solid-phase microextraction device for quantitative extraction of polycyclic aromatic hydrocarbons in sediment

A new automated headspace solid-phase microextraction (HS-SPME) sampling device was developed, with the capability of heating the sample matrix and simultaneously cooling the fiber coating. The device was evaluated for the quantitative extraction of polycyclic aromatic hydrocarbons (PAHs) from solid matrices. The proposed device improves the efficiency of the release of analytes from the matrix, facilitates the mass transfer into the headspace and significantly increases the partition coefficients of the analytes, by creating a temperature gap between the cold-fiber (CF) coating and the hot headspace. The reliability and applicability of previously reported cold-fiber devices are significantly enhanced by this improvement. In addition, it can be easily adopted for full automation of extraction, enrichment and introduction of different samples using commercially available autosampling devices. Sand samples spiked with PAHs were used as solid matrices and the effect of different experimental parameters were studied, including the extraction temperature, extraction time, moisture content, and the effect of sonication and modifier under optimal experimental conditions, linear calibration curves were obtained in the range of 0.0009-1000 ng/g, with regression coefficients higher than 0.99 and detection limits that ranged from 0.3 to 3 pg/g. Reproducible, precise and high throughput extraction, monitoring and quantification of PAHs were achieved with the automated cold-fiber headspace solid-phase microextraction (CF-HS-SPME) device coupled to GC-flame ionization detection. Determination of PAHs in certified reference sediments using the proposed approach exhibited acceptable agreement with the standard values.     

Determination of aflatoxins in peanuts by matrix solid-phase dispersion and liquid chromatography

A new method based on matrix solid-phase dispersion (MSPD) extraction was studied to determine aflatoxin B1, B2, G1 and G2 from peanuts. Optimization of different parameters, such as type of solid supports for matrix dispersion and elution solvents were carried out. The method used 2 g of peanut sample, 2 g of C18 bonded silica as MSPD sorbent and acetonitrile as eluting solvent. Recoveries of each aflatoxin spiked to peanut samples at 2.5 ng/g (5 ng/g for aflatoxin G2) level were between 78 and 86% with relative standard deviations ranging from 4 to 7%. The limits of quantification ranged from 0.125 to 2.5 ng/g for the four studied aflatoxins using liquid chromatography (LC) with fluorescence detection. In addition, LC coupled to mass spectrometry with an electrospray interface was used for confirmation of aflatoxins present in real samples. Eleven peanut samples from different countries were analyzed by the proposed method and by using an enzyme-linked immunosorbent assay (ELISA). ELISA test is a good screening method for investigation of these mycotoxins in peanut samples.     

Monitoring of PAHs in air by collection on XAD-2 adsorbent then microwave-assisted thermal desorption coupled with headspace solid-phase microextraction and gas chromatography with mass spectrometric detection

Microwave-assisted thermal desorption (MAD) coupled to headspace solid-phase microextraction (HS-SPME) has been studied for in-situ, one-step, sample preparation for PAHs collected on XAD-2 adsorbent, before gas chromatography with mass spectrometric detection. The PAHs on XAD-2 were desorbed into the extraction solution, evaporated into the headspace by use of microwave irradiation, and absorbed directly on a solid-phase microextraction fiber in the headspace. After desorption from the SPME fiber in the hot GC injection port, PAHs were analyzed by GC–MS. Conditions affecting extraction efficiency, for example extraction solution, addition of salt, stirring speed, SPME fiber coating, sampling temperature, microwave power and irradiation time, and desorption conditions were investigated. Experimental results indicated that extraction of 275 mg XAD-2, containing 10–200 ng PAHs, with 10-mL ethylene glycol–1 mol L⁻¹ NaCl solution, 7:3, by irradiation with 120 W for 40 min (the same as the extraction time), and collection with a PDMS–DVB fiber at 35 °C, resulted in the best extraction efficiency. Recovery was more than 80% and RSD was less than 14%. Optimum desorption was achieved by heating at 290 °C for 5 min. Detection limits varied from 0.02 to 1.0 ng for different PAHs. A real sample was obtained by using XAD-2 to collect smoke from indoor burning of joss sticks. The amounts of PAHs measured varied from 0.795 to 2.53 ng. The method is a simple and rapid procedure for determination of PAHs on XAD-2 absorbent, and is free from toxic organic solvents.     

Ultrasonication extraction coupled with magnetic solid-phase clean-up for the determination of polycyclic aromatic hydrocarbons in soils by high-performance liquid chromatography

C18-functionalized magnetic microspheres synthesized in a three-stage system and characterized by Fourier transform infrared (FTIR) spectroscopy and SEM were applied for clean-up and enrichment of polycyclic aromatic hydrocarbons (PAHs) in soil samples combined with ultrasonication extraction. Magnetic solid-phase extraction (MSPE) parameters, such as elution solvents, amounts of sorbents, enrichment time and organic modifier, were optimized together with ultrasonication time and extraction solvents. Under the optimal conditions, the developed method provided spiked recoveries of 63.2-92.8% with RSDs of less than 6.4% and limits of detection were 0.5-1.0 ng/g. This new method provides several advantages, such as high extraction efficiency, convenient extraction procedure and short analysis times. Finally, the method was successfully applied to the determination of polycyclic aromatic hydrocarbons in soil samples.     

Determination of nonylphenol and nonylphenol ethoxylates in environmental solid samples by ultrasonic-assisted extraction and high performance liquid chromatography-fluorescence detection

A simple and rapid analytical method for the determination of nonylphenol (NP) and nonylphenol ethoxylates (NPEOx) in solid environmental samples has been developed. This method combines an ultrasonic-assisted extraction procedure in small columns and an enrichment step onto C(18) solid-phase extraction cartridges prior to separation using HPLC with fluorescence detection. Method optimization was carried out using soil samples fortified at different concentration levels (from 0.1 to 100 microg/g). Under optimum conditions, 2g of soil was placed in small glass columns and extraction was performed assisted by sonication (SAESC) at 45 degrees C in two consecutive steps of 15 min using a mixture of H(2)O/MeOH (30/70). The obtained extracts were collected, loaded onto 500 mg C(18) cartridges, and analytes were eluted with 3 x 1 ml of methanol and 1 ml of acetonitrile. Finally, sample extracts were evaporated under a nitrogen stream, redissolved in 500 microl H(2)O/AcN (50/50), and passed though a 0.45 microm nylon filter before final determination by HPLC-FL. The developed procedure allowed to achieve quantitative recoveries for NP and NPEOx, and was properly validated. Finally, the method was applied to the determination of these compounds in soils and other environmental solid samples such as sediments, compost and sludge.     

Optimization and validation of HPLC-UV-DAD and HPLC-APCI-MS methodologies for the determination of selected PAHs in water samples

Polycyclic aromatic hydrocarbons (PAHs) are environmental contaminants resulting from emissions of a variety of sources including industrial combustion, discharge of fossil fuels, and residential heating. Because of their mutagenic and carcinogenic properties, the study of PAHs in environmental matrices is of great importance. In this work, the extraction of 9 out of the 16 PAH priority pollutants according to the U.S. Environmental Protection Agency is carried out through liquid-liquid extraction (LLE) and solid-phase extraction (SPE). The determination of PAHs is made by high-performance liquid chromatography with diode-array detection and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry. Between the extraction techniques used, LLE is revealed to be efficient in the extraction of the higher molecular weight PAHs, though SPE is adequate for the extraction of all PAHs. In the real water samples analyzed, no PAH is detected under the analysis conditions used.     

Analysis of polycyclic aromatic hydrocarbons in solid matrixes by solid-phase microextraction coupled to a direct extraction device

Analysis of polycyclic aromatic hydrocarbons (PAHs) standards in model systems was carried out by solid-phase microextraction (SPME) coupled to a direct extraction device (DED) and subsequent gas chromatography/mass spectrometry (GC/MS). PAHs standard was added to gelatine systems at different concentrations. Extraction process was carried out by SPME-DED at 25 °C for 60 min. Polydimethylsiloxane 100 μm (PDMS 100 μm), divinylbenzene/polydimethylsiloxane 65 μm (DVB/PDMS 65 μm) and polyacrilate 85 μm (PA 85 μm) SPME fibres were tested. SPME-DED satisfactorily extracted PAHs with a molecular weight (MW) lower than 206 from the gelatine system. All fibres showed a good reproducibility (residual standard deviation (RSD) between 5.24% and 18.25%), linearity (regression coefficients between 0.8959 and 0.9983) and limit of detection (LOD) (between 0.008 and 0.138 ng mL⁻¹). Presence of PAHs in different smoked meat products was also tested by SPME-DED. Different low MW PAHs were satisfactorily detected from all the foodstuffs studied. SPME-DED appears as a rapid, non-destructive technique for primary screening of low MW PAHs in solid matrixes.     

New micromethod combining miniaturized matrix solid-phase dispersion and in-tube in-valve solid-phase microextraction for estimating polycyclic aromatic hydrocarbons in bivalves

Miniaturized matrix solid-phase dispersion (MSPD) was developed for the extraction of common polycyclic aromatic hydrocarbons (PAHs) from bivalve samples (100mg, dry weight). Additional clean-up and analyte enrichment was accomplished by in-tube solid-phase microextraction (SPME). For this purpose the extracts collected after MSPD were diluted with water and injected into a capillary column coated with the extractive phase. This capillary column was connected to the analytical column by means of a switching valve. Separation and quantification of the PAHs were carried out using a monolithic LC column and fluorescence detection. Since the in-tube SPME device allowed the processing of large volumes of the extracts (2.0 mL) excellent sensitivity was achieved, thus making solvent evaporation operations unnecessary. The overall recoveries ranged from 10% to 28% for the studied compounds. The relative standard deviation (RSD) ranged from 2% to 10% for intra-day variation (n=3), and the limits of detection (LODs) were < or =0.6 ng/g (dry weight). The proposed procedure was very simple and rapid (total analysis time was approximately 20 min), and the consumption of organic solvents and extractive phases was drastically reduced. The reliability of the proposed MSPD/in-tube SPME method was tested by analysing several bivalves (mussels and tellins) as well as a standard reference material (SRM).     

羧基化多壁碳纳米管固相萃取-液相色谱-串联质谱法测定环境水体中四溴双酚A和双酚A

建立了羧基化碳纳米管固相萃取-液相色谱-串联质谱联用检测环境水体中四溴双酚A和双酚A的方法。比较了多壁碳纳米管、C60和羧基化多壁碳纳米管作为固相吸附剂对水体中四溴双酚A和双酚A的吸附效率。固相萃取浓缩后的样品经Thermo Scientific Hypersil C18色谱柱（150 mm×4.6 mm,3 μm）分离,采用串联质谱负离子模式进行检测。结果表明,四溴双酚A和双酚A在0.02~1.0 mg/L范围内具有良好的线性关系（r²≥0.99）,空白样品中的检出限（S/N=3）分别为0.04 μg/L和0.2 μg/L。将所建立的方法应用于实际环境水体中四溴双酚A和双酚A的检测,添加回收率在82%~99%之间,精密度小于5.0%,该方法可用于复杂环境样品中痕量四溴双酚A和双酚A的检测。     

Identification and quantitation of trenbolone in bovine tissue by gas chromatography-mass spectrometry

Identification and quantitation of trace amounts of trenbolone in bovine tissue by capillary gas chromatography-mass spectrometry-selected-ion monitoring (GC-MS-SIM) has been developed. Three-phase liquid-liquid extraction using a mixture of water-acetonitrile-dichloromethane-hexane was utilized for the sample extraction from tissue. Target compounds were extracted from the tissue into the acetonitrile layer. The residue from this extraction was then subjected to solid-phase extraction by C18 and silica gel disposable cartridges using methanol-water and benzene-acetone as eluents. To overcome extensive matrix interferences, preparative reversed-phase high-performance liquid chromatographic separation was used with an octadecyl-bonded column using methanol-water as mobile phase for sample clean-up prior to GC-MS analysis. A structural analogue of trenbolone, 19-nortestosterone, was chosen as the internal standard for quantitation by GC-MS. The sample was co-injected with N,O-bis (trimethylsilyl) trifluoroacetamide-1-(trimethylsilyl) imidazole (95:5, v/v) for flash heater derivation. Identification and quantitation were simultaneously carried out by SIM of characteristic ions of the trimethylsilyl derivatives of trenbolone and 19-nortestosterone. The limit of detection for trenbolone and epitrenbolone was 0.5 ppb in muscle and liver tissue. A comparison of sensitivity and specificity between GC-MS under electron ionization in addition to positive- and negative-ion chemical ionization conditions using methane reagent gas is also discussed.     

固相萃取-微乳液相色谱法测定环境水体中的3种酚类化合物

建立了固相萃取-微乳液相色谱法同时测定环境水体中的苯酚、双酚A (BPA)、2,4-二氯苯酚3种酚类化合物的检测方法。水样加酸酸化后,经C18固相萃取小柱富集净化,用微乳液相色谱法测定3种目标物的含量。在Inertsil C18色谱柱(150 mm×4.6 mm, 5 μm)上以微乳(3.0%十二烷基硫酸钠(SDS)-6.0%正丁醇-0.8%正庚烷-90.2%(水+0.5%HAc))和乙腈作为流动相进行梯度洗脱,流速1.0 mL/min,检测波长280 nm。结果表明,苯酚、双酚A、2,4-二氯苯酚的检出限(S/N=3)依次为0.74、8.0、8.0 μg/L,线性范围在0.1~10 mg/L范围内,相关系数(r)均大于0.999。将3种酚类化合物定量加到空白水样中,苯酚、双酚A、2,4-二氯苯酚的加标回收率分别为82.7%、87.8%、82.6%,其RSD均小于5%(n=6)。对环境水样的酚类化合物分析也取得了良好的加标回收率,其值均在85.7%~113.2%之间。结果表明,该方法准确可靠、灵敏度高,适用于环境水体中酚类化合物的检测。     

Assay of vecuronium in plasma using solid-phase extraction, high-performance liquid chromatography and post-column ion-pair extraction with fluorimetric detection

An assay has been developed and validated for the routine monitoring of vecuronium in plasma. It consists of solid-phase extraction using C18 disposables as sample pre-treatment, high-performance liquid chromatography and post-column ion-pair extraction with fluorimetric detection. The fluorescent anion 9,10-dimethoxyanthracene-2-sulphonate (DAS) is used as the counter ion. The detection limit is ca. 5 ng/ml in plasma with a signal-to-noise ratio of 10. The assay is also applicable for monitoring vecuronium and its potential metabolites in other biological media, e.g., urine, bile and tissue (liver, kidney) homogenates.     

Pyrrole-based conductive polymer as the solid-phase extraction medium for the preconcentration of environmental pollutants in water samples followed by gas chromatography with flame ionization and mass spectrometry detection

A pyrrole-based polymer was synthesized and applied as a new sorbent for solid-phase extraction (SPE) of some environmental pollutants from water samples. Polypyrrole (PPy) was synthesized by chemical oxidation of the monomer in nonaqueous solution. SPE of selected phenols, pesticides, and polyaromatic hydrocarbons (PAHs) from aqueous samples were performed using 200 mg PPy. The determination was subsequently carried out by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). The polymer showed much higher recoveries for aromatic compounds than aliphatics. Preconcentration of sample volumes up 11 led to acceptable recoveries for aromatic and other tested polar compounds. The R.S.D. for a river water sample spiked with phenols, pesticides and PAHs at sub-ppb level was lower than 10% (n = 3) and limits of detection for these compounds were between 15 and 120 ng l(-1).